A UN vaccine programme in Darfur in 2011. An innovative refrigeration system that doesn’t need a constant power supply is helping deliver vaccines to remote communities.
Photograph: Albert Gonzalez Farran/AFP/Getty

It was a walk past a frozen lake 10 years ago that got Ian Tansley thinking differently about global health. The Welsh inventor had spent decades travelling and developing solar technologies throughout Africa and Asia. Yet one puzzle he was keen to crack – how to deliver vaccines on a wide-scale basis to the poorest, most remote communities – had so far eluded him.

Vaccines are notoriously hard to deliver safely, requiring refrigeration at certain temperatures, which means having access to a constant power supply. Yet hot climates, intermittent availability of electricity, supply shortages and unreliable storage facilities mean that one in five children – more than 19m worldwide – do not get even the most basic immunisations to keep them healthy.

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Using the frozen lake as his inspiration, with its frozen top but liquid bottom, Tansley developed a refrigeration system, Sure Chill, that harnesses water’s unique properties to keep vaccines cool at 4C – yet doesn’t require a constant power supply. The refrigeration compartment is surrounded by water, and relies on the fact that the liquid is at its heaviest at 4C, when it sinks. When the device has power, the water cools and forms ice above the compartment, leaving only water at 4C cooling the contents. When the power is switched off, the water warms and rises while the ice begins to melt, and water at 4C remains below to keep the vaccines chilled.

Sure Chill – which was awarded a $1.5m (£1.2m) Grand Challenges grant from the Bill and Melinda Gates Foundation and is now used to deliver vaccines in 38 countries – has proved a major breakthrough in global health. Tansley’s immunisations cold-box can keep vaccines cool for up to 35 days in even 43C weather. And the technology is entirely scaleable, from a cool box up to a warehouse.

Naming it one of the top four innovations saving children’s lives, the Gates Foundation’s director of vaccine delivery, Dr Orin Levine, calls Sure Chill “an important tool in humanitarian response efforts” and says it demonstrates, for the first time in decades, a global health issue “benefiting from significant innovation”.

Innovation is the theme of this year’s Grand Challenges global conference, taking place in London this week. Experts from all over the world will address key questions in tackling global health challenges, including innovations in achieving the sustainable development goals, treating infectious diseases, and developing collaborations between north and south.

Equally problematic in the global health challenge is poor sanitation: 40% of the world’s population currently lacks adequate toilet facilities, which in turn contributes to poor health and devastating environmental impacts.

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Loowatt was granted a $1.3m investment to develop a waterless toilet system. Developed by Virginia Gardiner, an American journalist-turned-industrial design engineer, Loowatt has had a massive impact in Madagascar, where a pilot public toilet project has grown to provide 100 toilets for private use within family homes, and is set to be rolled out across other countries in sub-Saharan Africa.

The toilets seal waste into a portable cartridge within biodegradable film, and combine anaerobic digestion with pasteurisation in order to kill off any waterborne diseases. The waste is collected and converted into fertiliser and biogas, which is then used for cooking and electricity.

The toilets are particularly essential in regions where waterborne diseases are prevalent, or where shared – or a complete lack of – toilets prevent women and girls from going to the bathroom, says Gardiner.

“People are going from having pit latrines at home to our toilets in their homes, which means they’re not being exposed to eco-pathogens in their everyday lives any more,” says Gardiner. “The current model can support 2,000 people – in urban or rural settings – and is important in showing that in this global sanitation crisis, there is technology out there than can convert waste into energy.”

Both Gardiner’s and Tansley’s systems get to the heart of what the Grand Challenges are about – improving the lives of the world’s most vulnerable. Tansley has been surprised at just how much his Sure Chill technology has changed the face of medical outreach. “The people benefiting the most are generally the poorest people in the most remote places, the people you just wouldn’t normally see: rural agricultural communities far from any infrastructure or power grid,” he says. “Maybe they’re nomadic or very dispersed – they’re people who weren’t being reached before.”